WASHINGTON  A type of caterpillar with a taste for escargot rather than the normal vegetable diet has been discovered in Hawaii.

The caterpillar is the first ever observed to eat any kind of mollusk, researchers report in Friday's issue of the journal Science.

Indeed, only about one-tenth of 1 percent of caterpillars eat anything but vegetables.

Hyposmocoma molluscivora, however, will not eat the green stuff even when the caterpiller is starving, say Daniel Rubinoff and William P. Haines of the University of Hawaii, Honolulu.

When these caterpillars come across a resting snail, they begin spinning silk of the type they use to make their cocoons. They wrap the silk around the snail, trapping it so the snail cannot escape by dropping off the leaf.

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Then, the researchers say, it's snail-snacking time.

"They wrap 'em, up and then they go in, the snail doesn't really have a chance," Rubinoff said in a telephone interview.

The caterpillar "wedges its case next to or inside the snail shell and stretches much of its body out of the silk case, pursuing the retreating snail to the end of the shell from which there is no escape," Haines and Rubinoff report.

The researchers observed 18 different snail attacks by 10 different caterpillars.

The snails they studied were on Maui, but Rubinoff said others have since been found on three other Hawaiian islands -- Molokai, Hawaii and Kauai.

A few caterpillars have been found to eat scale and other small insects but moving on to snails is a big shift, he said.

"I don't think we have any idea how something like that happens," Rubinoff said when asked how these caterpillars might have started on such a diet. "It's one of the things that makes Hawaii such a great place to do this research," he said, adding that there are probably a lot more unusual creatures waiting to be discovered.

Finding something like this "just never occurred to us," Rubinoff said. "Just because we didn't think of it doesn't mean its not right there."